'I wasn't saying it would make it impossible to play on the harp. '

The way I read descriptions of what Bunting did, did indeed suggest he added incidentals not only alien to the original music but also unavailable on the harp.

The key signatures are easily explained: harpers didn't necessarily tune to a set pitch and he took down the key signature of what he actually heard, rather than taking account the tuning of the harp. Some collectors treated music they heard played on the flat pipes in a similar way.